Specifically, the number of credit card transactions per U.S. resident grew from fewer than 20 in 1990 to more than 80 by the mid-2000s—or from once every three weeks to once every four days.

'The new payment mix is more about market share than about which payment dominates or will dominate.'

The number of debit card transactions per U.S. resident grew even faster, from one in 1990 to 118 in 2009—or from once every year to once every three days.

"The new payment mix is more about market share than about which payment dominates or will dominate,” says Ben Rogers, Filene research director. “Credit unions care deeply about whether consumers use debit and credit cards.” In addition to the loyalty they create, plastic cards are among the few revenue centers credit unions can influence, he says.

Debit cards are in use in 71% of American households, but only 19% of consumer households use them as a primary payment method, according to the report. This research indicates as income and net worth increase, so does credit card use. This might be the vestige of a system of loose credit and attractive credit card rewards.

But if the new credit card rules substantially limit the rewards companies offer to cardholders, says the report, debit use could catch up. If not, the economic advantages of nonrevolving credit card use could keep credit cards at the top of the payment heap for middle- to high-income consumers. Credit cards are a mature product, entrenched but unlikely to surge ever again.

Next: Other report findings

Other report findings include:

Debit cards have been used by over half of U.S. households for barely a decade, and there’s no evidence that a peak in debit use is imminent.

Intensive credit card users have both higher incomes and higher debt levels than those with neither card and those with only debit cards. They also have higher household net worth and a higher net worth-to-income ratio.

Intensive debit card users are generally younger. Debit-only users decrease by age, from 29% of 18- to 29-year-olds to just 7% of those over age 70. Conversely, credit-only users increase by age, from 29% of 18- to 29-year-olds to 49% of those over 70.

The fraction of households using electronic billing, like many other recent technologies outside the payment arena, has grown much faster than those for earlier technological innovations, growing apace from near obscurity to near ubiquity—4% of households in 1995 to 53% in 2007.

The Filene report illuminates the often irrational ways consumers choose payment methods. But what might be perfectly rational reasons for using a credit card (interest-free loans for nonrevolvers and generous rewards) might not account for those who use debit to control spending or to avoid the danger of revolving debt. New overdraft regulations could also make debit simpler and more attractive for everyday users.

And as ever-more sophisticated and niche payment systems (virtual currencies, social payments, ACH iterations) emerge, credit unions will need to pay attention to consumer demands and trends. “It’s entirely possible that 10 years from now, our cell phone-transacting children will stare blankly as we talk about choosing between credit and debit cards,” says Rogers.

Rather than predicting the imminent demise of this or that payment method, though, the Filene research encourages credit unions to recognize that a complex mix of payments—each attuned to the context and convenience of the purchase—is here to stay.